Hot-pressing apparatus

ABSTRACT

Disclosed is a hot-pressing apparatus capable of quenching a workpiece at a sufficient cooling rate. The hot-pressing apparatus performs a hot-press forming of a workpiece using a lower die and an upper die, in which a cooling channel and a cooling channel, and a plurality of gas-introduction paths and a plurality of gas-introduction paths through which heat-conducting gas flows are provided in the lower die and the upper die. The plurality of gas-introduction paths penetrate through the dies. The hot-press forming is performed while the heat-conducting gas is supplied to the areas between the dies and the workpiece from the plurality of gas-introduction paths opening on the forming surfaces of the dies.

TECHNICAL FIELD

The present invention relates to a hot-pressing apparatus which presses and cools a heated workpiece at the same time.

BACKGROUND ART

Conventionally, a hot-pressing apparatus is widely known which causes a die to press a workpiece, such as a steel plate, heated to above a temperature at which an austenite structure appears, and at the same time, quenches the workpiece by bring the die into contact with the workpiece.

A technique on the hot-pressing apparatus is publicly known which enables the die to suitably cool the workpiece during the quenching by providing water channels through which cooling water to cool the die flows in the die (for example, see Patent Literature 1).

However, since the pressed workpiece deforms because of spring back, uneven thickness thereof and the like, a gap is formed between the workpiece and the die during the quenching. Consequently, a contact area between the surface of the workpiece and the forming surface of the die decreases during the quenching, which causes a problem that some parts in the workpiece are not cooled at a sufficient cooling rate (e.g. 30 [° C./sec] and above), and hardness of some parts in the workpiece is smaller than a predetermined value.

CITATION LIST Patent Literature

Patent Literature 1: JP 2006-326620 A

SUMMARY OF INVENTION Problem to Be Solved By the Invention

The objective of the present invention is to provide a hot-pressing apparatus capable of quenching a workpiece at a sufficient cooling rate.

Means for Solving the Problem

The first embodiment of the present invention is a hot-pressing apparatus including a lower die having a lower forming surface, and an upper die having an upper forming surface facing the lower forming surface, which performs a hot-press forming in which the lower die and the upper die press a heated workpiece arranged therebetween, and at the same time, the forming surfaces of the lower die and the upper die are kept in contact with a surface of the workpiece to cool the workpiece. The lower die and/or the upper die includes a cooling channel through which a cooling medium flows, and a plurality of gas-introduction paths through which heat-conducting gas flows. The plurality of gas-introduction paths penetrate through the lower die and/or the upper die from the forming surface thereof to a surface other than that forming surface. The hot-press forming is performed while the heat-conducting gas is supplied to an area between the workpiece and the lower die and/or the upper die from the plurality of gas-introduction paths opening on the forming surface of the lower die and/or the upper die.

Advantageously, the plurality of gas-introduction paths are formed to run in the vicinity of the cooling channel.

Preferably, the plurality of gas-introduction paths open on the forming surface of the lower die and/or the upper die so as to coincide in position with gaps formed by deformation of the pressed workpiece between the workpiece and the lower die and/or the upper die where the plurality of gas-introduction paths are formed.

Effects of the Invention

The present invention makes it possible to quench a workpiece at a sufficient cooling rate, and to prevent hardness of some parts in the workpiece from being smaller than a predetermined value.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a hot-pressing apparatus according to an embodiment of the present invention.

FIG. 2 illustrates the hot-pressing apparatus in which an upper die moves to the bottom dead center when pressing a workpiece.

FIG. 3 illustrates the hot-pressing apparatus in which the upper die is at the bottom dead center when pressing the workpiece.

DESCRIPTION OF EMBODIMENTS

With reference to FIGS. 1 to 3, described below is a hot-pressing apparatus 1 as an embodiment of a hot-pressing apparatus according to the present invention.

The hot-pressing apparatus 1 performs hot-press forming of a workpiece W.

The workpiece W is a steel plate to be pressed by the hot-pressing apparatus 1, and is heated to above a temperature at which an austenite structure appears by ohmic heating and the like.

For convenience, a top-bottom direction in FIG. 1 is defined as a top-bottom direction of the hot-pressing apparatus 1, and a right-left direction in FIG. 1 is defined as a right-left direction of the hot-pressing apparatus 1. In addition, this side in FIG. 1 is defined as a front side of the hot-pressing apparatus 1, and the far side in FIG. 1 is defined as a rear side of the hot-pressing apparatus 1, thereby a front-rear direction of the hot-pressing apparatus 1 being defined.

As shown in FIG. 1, the hot-pressing apparatus 1 includes a lower die 10, an upper die 20, two lateral gas-feeders 30, a lower gas-feeder 40, and an upper gas-feeder 50.

The lower die 10 and the upper die 20 are arranged so that the forming surfaces thereof are opposed to each other. The upper die 20 is brought close to the lower die 10 by a hydraulic cylinder and the like to move to the bottom dead center. Thereby, the lower die 10 and the upper die 20 press the workpiece W arranged therebetween to form the workpiece W into what is called a hat shape. At the same time, the lower die 10 and the upper die 20 keep the forming surfaces thereof in contact with the surface of the workpiece W to cool the workpiece W. Consequently, the workpiece W as a product is produced.

The lower die 10 corresponds to the upper die 20. The lower die 10 has a protrusion 11 which protrudes upward from the forming surface (the upper surface) thereof.

The protrusion 11 protrudes upward from the forming surface of the lower die 10. The protrusion 11 is continuously formed in the front-rear direction in the intermediate part (the substantially middle part), in the right-left direction, of the forming surface of the lower die 10.

The lower die 10 has a top surface 10 a extending in the right-left direction at the uppermost part of the protrusion 11, two lateral surfaces 10 b extending downward from both the ends of the top surface 10 a in the right-left direction, and two base surfaces 10 c extending outward in the right-left direction from the bottom ends of the lateral surfaces 10 b, and these surfaces act as what is called a hat-shaped forming surface of the lower die 10.

The lower die 10 has a cooling channel 12, a plurality of gas-introduction paths 13, a plurality of gas-introduction paths 14, and a plurality of gas-introduction paths 15 which are provided inside the lower die 10.

The cooling channel 12 is a channel through which a cooling medium such as water flows, and is provided in the lower die 10 to cool the forming surface of the lower die 10. The cooling channel 12 is configured so that the cooling medium flows into the lower die 10 through the lower surface of the right part of the lower die 10, and then flows to the outside of the lower die 10 through the lower surface of the left part of the lower die 10 after flowing inside the lower die 10 in the front-rear direction and the right-left direction (see the white-painted arrows in FIG. 1). Note that a predetermined pump (not shown) enables the cooling medium to flow in the lower die 10. After the cooling medium cools the forming surface of the lower die 10 and flows to the outside of the lower die 10, the cooling medium is cooled and flows into the lower die 10 again. Thus, the cooling medium constantly circulates in the lower die 10.

The gas-introduction path 13, the gas-introduction path 14 and the gas-introduction path 15 are paths through which helium gas flows which is inert gas (hereinafter referred to as “heat-conducting gas”) with thermal conductivity extremely higher than that of air. The gas-introduction path 13, the gas-introduction path 14 and the gas-introduction path 15 are bored through the lower die 10 in the top-bottom direction from the forming surface to the lower surface of the lower die 10, and are formed to run the vicinity of the cooling channel 12. The gas-introduction path 13, the gas-introduction path 14 and the gas-introduction path 15 open on the middle of the top surface 10 a in the right-left direction, on the part of the left base surface 10 c in the vicinity of the left lateral surface 10 b, and on the part of the right base surface 10 c in the vicinity of the right lateral surface 10 b, respectively. Note that, although not shown, each of the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 are formed in the lower die 10 at predetermined intervals in the front-rear direction.

As mentioned above, in the lower die 10, the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 are formed on three places in total: the middle of the top surface 10 a in the right-left direction, and the parts of the base surfaces 10 c in the vicinities of the lateral surfaces 10 b.

Note that each of the openings, which open on the forming surface of the lower die 10, of the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 formed in the lower die 10 has such an inner diameter that the openings have no negative influence on the press working of the workpiece W (that the press working of the workpiece W is performed similarly to a conventional press working thereof).

The upper die 20 corresponds to the lower die 10. The upper die 20 has a recess 21 in which the forming surface (the lower surface) of the upper die 20 dents upward along the shape of the protrusion 11.

The recess 21 is formed so that the forming surface of the upper die 20 dents upward. The recess 21 is continuously formed in the front-rear direction in the intermediate part (the substantially middle part), in the right-left direction, of the forming surface of the upper die 20.

The upper die 20 has a bottom surface 20 a extending in the right-left direction at the uppermost part of the recess 21, two lateral surfaces 20 b extending downward from both the ends of the bottom surface 20 a in the right-left direction, and two base surfaces 20 c extending outward in the right-left direction from the bottom ends of the lateral surfaces 20 b, and these surfaces act as what is called a hat-shaped forming surface of the upper die 20.

The upper die 20 has a cooling channel 22, a plurality of gas-introduction paths 23, a plurality of gas-introduction paths 24, a plurality of gas-introduction paths 25, and a plurality of gas-introduction paths 26 which are arranged inside the upper die 20.

The cooling channel 22 is a channel through which the cooling medium such as water flows, and is provided in the upper die 20 to cool the forming surface of the upper die 20. The cooling channel 22 is configured so that the cooling medium flows into the upper die 20 through the upper surface of the right part of the upper die 20, and then flows to the outside of the upper die 20 through the upper surface of the left part of the upper die 20 after flowing inside the upper die 20 in the front-rear direction and the right-left direction (see the white-painted arrows in FIG. 1). Note that a predetermined pump (not shown) enables the cooling medium to flow in the upper die 20. After the cooling medium cools the forming surface of the upper die 20 and flows to the outside of the upper die 20, the cooling medium is cooled and flows into the upper die 20 again. Thus, the cooling medium constantly circulates in the upper die 20.

The gas-introduction path 23, the gas-introduction path 24, the gas-introduction path 25 and the gas-introduction path 26 are paths through which the helium gas as the heat-conducting gas flows. The gas-introduction path 23, the gas-introduction path 24, the gas-introduction path 25 and the gas-introduction path 26 are bored through the upper die 20 in the top-bottom direction from the forming surface to the upper surface of the upper die 20, and are formed to run the vicinity of the cooling channel 22. The gas-introduction path 23, the gas-introduction path 24, the gas-introduction path 25 and the gas-introduction path 26 open on the part of the bottom surface 20 a in the vicinity of the left lateral surface 20 b, on the part of the bottom surface 20 a in the vicinity of the right lateral surface 20 b, the part of the left base surface 20 c in the vicinity of the left lateral surface 20 b, and the part of the right base surface 20 c in the vicinity of the right lateral surface 20 b, respectively. Note that, although not shown, each of the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 are formed in the upper die 20 at predetermined intervals in the front-rear direction.

As mentioned above, in the upper die 20, the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 are formed on four places in total: the parts of the bottom surface 20 a in the vicinities of the lateral surfaces 20 b, and the parts of the base surfaces 20 c in the vicinities of the lateral surfaces 20 b.

Note that each of the openings, which open on the forming surface of the upper die 20, of the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 formed in the upper die 20 has such an inner diameter that the openings have no negative influence on the press working of the workpiece W (that the press working of the workpiece W is performed similarly to a conventional press working thereof).

The lateral gas-feeders 30 are devices for feeding the helium gas as the heat-conducting gas to an area between the lower die 10 and the upper die 20 (to an area between the workpiece W and the lower die 10, and an area between the workpiece W and the upper die 20). The lateral gas-feeders 30 discharge the helium gas as the heat-conducting gas stored in a predetermined container (not shown) into the area between the lower die 10 and the upper die 20. The lateral gas-feeders 30 are arranged to the left and the right of the lower die 10 in the vicinities of the base surfaces 10 c of the lower die 10 so as to discharge the helium gas as the heat-conducting gas into the space between the lower die 10 and the upper die 20 from the outside of the lower die 10 and the upper die 20 when the upper die 20 arrives at the bottom dead center (see FIG. 3). Note that, although not shown, each of the lateral gas-feeders 30 has a plurality of nozzles from which the helium gas as the heat-conducting gas discharges, and the plurality of nozzles are arranged at predetermined intervals in the front-rear direction.

The lower gas-feeder 40 is a device for feeding the helium gas as the heat-conducting gas to an area between the workpiece W and the lower die 10. Specifically, the lower gas-feeder 40 causes the helium gas as the heat-conducting gas stored in a predetermined container (not shown) to flow into the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 formed in the lower die 10 from the openings on the lower surface of the lower die 10, and to spout from the openings on the forming surface of the lower die 10.

The upper gas-feeder 50 is a device for feeding the helium gas as the heat-conducting gas to an area between the workpiece W and the upper die 20. Specifically, the upper gas-feeder 50 causes the helium gas as the heat-conducting gas stored in a predetermined container (not shown) to flow into the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 formed in the upper die 20 from the openings on the upper surface of the upper die 20, and to spout from the openings on the forming surface of the upper die 20.

Described below is behavior of the hot-pressing apparatus 1 configured as mentioned above during the hot-press forming of the workpiece W.

As shown in FIG. 2, the upper die 20 moves toward the lower die 10 to press the workpiece W. Then, before the upper die 20 arrives at the bottom dead center, the lateral gas-feeders 30 feed the helium gas as the heat-conducting gas to the area between the lower die 10 and the upper die 20, the lower gas-feeder 40 feeds the helium gas as the heat-conducting gas to the area between the workpiece W and the lower die 10, and the upper gas-feeder 50 feeds the helium gas as the heat-conducting gas to the area between the workpiece W and the upper die 20.

Note that black-painted arrows in FIG. 2 show directions in which the helium gas as the heat-conducting gas discharges.

As shown in FIG. 3, until the upper die 20 arrives at the bottom dead center, the lateral gas-feeders 30, the lower gas-feeder 40 and the upper gas-feeder 50 continue to feed the helium gas as the heat-conducting gas. Thus, the upper die 20 is kept at the bottom dead center in the state where the helium gas as the heat-conducting gas fills the area between the workpiece W and the lower die 10, and the area between the workpiece W and the upper die 20.

Note that timing when the lateral gas-feeders 30, the lower gas-feeder 40 and the upper gas-feeder 50 feed the helium gas as the heat-conducting gas is not limited as long as the helium gas as the heat-conducting gas fills the area between the workpiece W and the lower die 10, and the area between the workpiece W and the upper die 20 when the upper die 20 is kept at the bottom dead center.

Since the pressed workpiece W slightly deforms because of spring back and the like, gaps are formed between the lower die 10 and the upper die 20.

However, when the lower die 10 and the upper die 20 cool the workpiece W, the helium gas with thermal conductivity extremely higher than that of air fills the area between the workpiece W and the lower die 10, and the area between the workpiece W and the upper die 20. This makes it possible to quench even a part of the workpiece W separate from the forming surface of the lower die 10 or the forming surface of the upper die 20 at a sufficient cooling rate (e.g. 30 [° C./sec] and above).

Therefore, it is possible to prevent hardness of some parts in the workpiece W from being smaller than a predetermined value.

Moreover, it is possible to control oxidation of the lower die 10 and the upper die 20 to a minimum because the helium gas is inert gas difficult to undergo chemical reactions.

Hydrogen gas with thermal conductivity comparable to that of the helium gas may be given as the heat-conducting gas according to the present invention in addition to the helium gas. However, it is preferable that the helium gas which is inert gas is adopted because the hydrogen gas is easy to undergo chemical reactions.

On the other hand, nitrogen gas, argon gas and the like may be given as inert gas. However, these gases are excluded because each of these gases has thermal conductivity comparable to that of air.

As mentioned previously, the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 are formed in the lower die 10, and the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 are formed in the upper die 20.

Thus, when the helium gas as the heat-conducting gas discharged from the lower gas-feeder 40 flows through the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15, the lower die 10 cooled by the cooling channel 12 cools the helium gas. In addition, when the helium gas as the heat-conducting gas discharged from the upper gas-feeder 50 flows through the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26, the upper die 20 cooled by the cooling channel 22 cools the helium gas.

Therefore, the helium gas as the heat-conducting gas can be cooled without using a device for cooling the helium gas as the heat-conducting gas, and the helium gas as the heat-conducting gas can quickly remove heat of the workpiece W when the workpiece W is quenched.

The plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 are formed to run the vicinity of the cooling channel 12, and the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 are formed to run the vicinity of the cooling channel 22.

Thus, when the helium gas as the heat-conducting gas discharged from the lower gas-feeder 40 flows through the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15, the helium gas is cooled by the cooling channel 12. In addition, when the helium gas as the heat-conducting gas discharged from the upper gas-feeder 50 flows through the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26, the helium gas is cooled by the cooling channel 22.

Therefore, the helium gas as the heat-conducting gas can more quickly remove heat of the workpiece W when the workpiece W is quenched.

It is desirable that the gas-introduction path 13, the gas-introduction path 14 and the gas-introduction path 15 are formed so as to have as many parts in the vicinity of the cooling channel 12 as possible. In addition, it is desirable that the gas-introduction path 23, the gas-introduction path 24, the gas-introduction path 25 and the gas-introduction path 26 are formed so as to have as many parts in the vicinity of the cooling channel 22 as possible.

The plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 are formed to open on the forming surface of the lower die 10, and the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 are formed to open on the forming surface of the upper die 20.

Thus, the helium gas as the heat-conducting gas discharged from the lower gas-feeder 40 can spout from the openings on the forming surface of the lower die 10, and the helium gas as the heat-conducting gas discharged from the upper gas-feeder 50 can spout from the openings on the forming surface of the upper die 20.

Therefore, the helium gas as the heat-conducting gas can efficiently be supplied to the area between the workpiece W and the lower die 10, and the area between the workpiece W and the upper die 20 without the helium gas diffusing to the atmosphere, compared with the case where the helium gas is supplied from a place, for example, situated sideward of the workpiece W.

The plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 are formed on the middle of the top surface 10 a in the right-left direction, and on the parts of the base surfaces 10 c in the vicinities of the lateral surfaces 10 b. In addition, the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 are formed on the parts of the bottom surface 20 a in the vicinities of the lateral surfaces 20 b, and on the parts of the base surfaces 20 c in the vicinities of the lateral surfaces 20 b. In other words, as shown in FIG. 3, the plurality of gas-introduction paths 13, the plurality of gas-introduction paths 14 and the plurality of gas-introduction paths 15 open on the forming surface of the lower die 10 so as to coincide in position with the gaps between the pressed workpiece W and the lower die 10. In addition, the plurality of gas-introduction paths 23, the plurality of gas-introduction paths 24, the plurality of gas-introduction paths 25 and the plurality of gas-introduction paths 26 open on the forming surface of the upper die 20 so as to coincide in position with the gaps between the pressed workpiece W and the upper die 20.

This makes it possible to efficiently supply the helium gas as the heat-conducting gas to the area between the workpiece W and the lower die 10, and the area between the workpiece W and the upper die 20, and to fill the area between the workpiece W and the lower die 10, and the area between the workpiece W and the upper die 20 with the helium gas in a small mount.

Therefore, it is possible to control consumption of the helium gas as the heat-conducting gas to a minimum, and to reduce costs.

Note that positions of the gaps between the workpiece W and the lower die 10, and the gaps between the workpiece W and the upper die 20 can be grasped in advance because deformation characteristics of the pressed workpiece W can be acquired through experiment and the like.

In the present embodiment, each of the lower die 10 and the upper die 20 is provided with a cooling channel and a plurality of gas-introduction paths, but one of the lower die 10 and the upper die 20 may be provided with the cooling channel and the plurality of gas-introduction paths.

Moreover, in the present embodiment, the lower die 10 and the upper die 20 have shapes to form the workpiece W into the hat shape, but the shapes thereof are not limited thereto. The present invention may be applied to a hot-pressing apparatus including a lower die and an upper die with other shapes.

In the present embodiment, a gas-feeder according to the present invention consists of the lateral gas-feeders 30, the lower gas-feeder 40 and the upper gas-feeder 50, but these may be configured as one gas-feeder.

INDUSTRIAL APPLICABILITY

The present invention is applied to a hot-pressing apparatus which presses and cools a heated workpiece at the same time.

REFERENCE SIGNS LIST

-   1: hot-pressing apparatus -   10: lower die -   12: cooling channel -   13, 14, 15: gas-introduction path -   20: upper die -   22: cooling channel -   23, 24, 25, 26: gas-introduction path -   30: lateral gas-feeder -   40: lower gas-feeder -   50: upper gas-feeder 

1. A hot-pressing apparatus comprising a lower die having a lower forming surface, and an upper die having an upper forming surface facing the lower forming surface, which performs a hot-press forming in which the lower die and the upper die press a heated workpiece arranged therebetween, and at the same time, the forming surfaces of the lower die and the upper die are kept in contact with a surface of the workpiece to cool the workpiece, wherein the lower die and/or the upper die comprises: a cooling channel through which a cooling medium flows; and a plurality of gas-introduction paths through which heat-conducting gas flows, the plurality of gas-introduction paths penetrate through the lower die and/or the upper die from the forming surface thereof to a surface other than that forming surface so as to run in the vicinity of the cooling channel, and open on the forming surface of the lower die and/or the upper die so as to coincide in position with gaps formed by deformation of the pressed workpiece between the workpiece and the lower die and/or the upper die where the plurality of gas-introduction paths are formed, and the hot-press forming is performed while the heat-conducting gas is supplied to an area between the workpiece and the lower die and/or the upper die from the plurality of gas-introduction paths. 2-3. (canceled) 